%   - - - - - - - - - -
%    i a u N u t 0 6 a
%   - - - - - - - - - -
% 
%   IAU 2000A nutation with adjustments to match the IAU 2006
%   precession.
% 
%   Given:
%      date1,date2      TT as a 2-part Julian Date (Note 1)
% 
%   Returned:
%      dpsi,deps        nutation, luni-solar + planetary (Note 2)
% 
%   Status:  canonical model.
% 
%   Notes:
%   1) The TT date date1+date2 is a Julian Date, apportioned in any
%      convenient way between the two arguments.  For example,
%      JD(TT)=2450123.7 could be expressed in any of these ways,
%      among others:
% 
%             date1          date2
% 
%          2450123.7           0.0       (JD method)
%          2451545.0       -1421.3       (J2000 method)
%          2400000.5       50123.2       (MJD method)
%          2450123.5           0.2       (date & time method)
% 
%      The JD method is the most natural and convenient to use in
%      cases where the loss of several decimal digits of resolution
%      is acceptable.  The J2000 method is best matched to the way
%      the argument is handled internally and will deliver the
%      optimum resolution.  The MJD method and the date & time methods
%      are both good compromises between resolution and convenience.
% 
%   2) The nutation components in longitude and obliquity are in radians
%      and with respect to the mean equinox and ecliptic of date,
%      IAU 2006 precession model (Hilton et al. 2006, Capitaine et al.
%      2005).
% 
%   3) The function first computes the IAU 2000A nutation, then applies
%      adjustments for (i) the consequences of the change in obliquity
%      from the IAU 1980 ecliptic to the IAU 2006 ecliptic and (ii) the
%      secular variation in the Earth's dynamical form factor J2.
% 
%   4) The present function provides classical nutation, complementing
%      the IAU 2000 frame bias and IAU 2006 precession.  It delivers a
%      pole which is at current epochs accurate to a few tens of
%      microarcseconds, apart from the free core nutation.
% 
%   Called:
%      iauNut00a    nutation, IAU 2000A
% 
%   References:
%      Chapront, J., Chapront-Touze, M. & Francou, G. 2002,
%      Astron.Astrophys. 387, 700
% 
%      Lieske, J.H., Lederle, T., Fricke, W. & Morando, B. 1977,
%      Astron.Astrophys. 58, 1-16
% 
%      Mathews, P.M., Herring, T.A., Buffet, B.A. 2002, J.Geophys.Res.
%      107, B4.  The MHB_2000 code itself was obtained on 9th September
%      2002 from ftp//maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
% 
%      Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
%      Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
% 
%      Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
%      Astron.Astrophys.Supp.Ser. 135, 111
% 
%      Wallace, P.T., "Software for Implementing the IAU 2000
%      Resolutions", in IERS Workshop 5.1 (2002)
% 
%   This revision:  2011 April 3
% 
%   SOFA release 2012-03-01
% 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function [dpsi, deps] = iauNut06a(date1, date2)

global const

% Interval between fundamental date J2000.0 and given date (JC).
t = ((date1 - const.DJ00) + date2) / const.DJC;

% Factor correcting for secular variation of J2.
fj2 = -2.7774e-6 * t;

% Obtain IAU 2000A nutation.
[dp, de] = iauNut00a(date1, date2);

% Apply P03 adjustments (Wallace & Capitaine, 2006, Eqs.5).
dpsi = dp + dp * (0.4697e-6 + fj2);
deps = de + de * fj2;

